Absorption mechanisms in macroporous silicon photonic crystals

Photoconductivity Relaxation Time in Macroporous Silicon

“…The relative relaxation time of photoconductivity is determined from expression (23), rewritten as follows: The characteristic number as characterizes the influence of surface and does not depend on bulk lifetime. It depends on the sample thickness, pore depth, surface recombination rate, diffusion coefficient, and other quantities, as can be seen from expressions (19)(20)(21)(22). It can be seen from expression (24) that the bulk lifetime and characteristic number as are in the denominator; therefore, with an increase in these values, the relative relaxation time of photoconductivity in macroporous silicon will decrease, which we observe in Figures 4 to 9.…”

“…It can be seen from expression (24) that the bulk lifetime and characteristic number as are in the denominator; therefore, with an increase in these values, the relative relaxation time of photoconductivity in macroporous silicon will decrease, which we observe in Figures 4 to 9. The characteristic number as is proportional to the surface recombination rate, as can be seen from expressions (19)(20)(21)(22). It grows with increasing depth of macropores, because recombination on the surface of macropores increases with increasing depth of macropores.…”

“…Absorption in macroporous silicon and macroporous silicon photonic crystals is due to absorption on free carriers and Lambertian light trapping. Numerical modeling showed that Lambertian light trapping is the predominant absorption mechanism in the band gap region [20].…”

The Influence of Preparation Parameters on Structural and Optical Properties of N-Type Porous Silicon

“…Macroporous silicon (MPS) is a novel material described as such in the early 1990s by Lehmann et al in their pioneering works [8]- [10] which invented an electrochemical etching process to produce arrays of ordered macropores in silicon [6]. Since its first description, MPS has attracted great interest, and it has been suggested for many applications in several fields such as electronics [11], optics [5], photonics [12] solar cells [13] , and even energy storage [14] fuel cells [6] or catalysis [15] Several methods for the fabrication of ordered MPS have been used such as reactive ion etching, stain etching [16],metal assisted etching [17], direct laser writing (DLW) [18], lithographic methods (layer-by-layer [19], interference lithography [20], block copolymer [21]) and glancing angle deposition [22] However, the electrochemical etching of silicon remains one of the most important and versatile fabrication methods. In this method, the MPS layer is formed on the crystalline silicon (c-Si) by anodic electrochemical etching in aqueous hydrofluoric (HF) solution [23].…”